Chondrocyte hypertrophy is one of the key indicators in the progression of osteoarthritis (OA). However, compared with other OA indications, such as cartilage collapse, sclerosis, inflammation, and protease activation, the mechanisms by which chondrocyte hypertrophy contributes to OA remain elusive. As the pathological processes in the OA cartilage microenvironment, such as the alterations in the extracellular matrix, are initiated and dictated by the physiological state of the chondrocytes, in-depth knowledge of chondrocyte hypertrophy is necessary to enhance our understanding of the disease pathology and develop therapeutic agents. Chondrocyte hypertrophy is a factor that induces OA progression; it is also a crucial factor in the endochondral ossification. This review elaborates on this dual functionality of chondrocyte hypertrophy in OA progression and endochondral ossification through a description of the characteristics of various genes and signaling, their mechanism, and their distinguishable physiological effects. Chondrocyte hypertrophy in OA progression leads to a decrease in chondrogenic genes and destruction of cartilage tissue. However, in endochondral ossification, it represents an intermediate stage at the process of differentiation of chondrocytes into osteogenic cells. In addition, this review describes the current therapeutic strategies and their mechanisms, involving genes, proteins, cytokines, small molecules, three-dimensional environments, or exosomes, against the OA induced by chondrocyte hypertrophy. Finally, this review proposes that the contrasting roles of chondrocyte hypertrophy are essential for both OA progression and endochondral ossification, and that this cellular process may be targeted to develop OA therapeutics.

BACKGROUND : Extracellular vesicles (EVs) have attracted expanded attention as vehicles for the diagnosis and therapy of diseases and regenerative medicine due to their biocompatibility, efficient cellular uptake ability, and capacity to transport biologically active molecules. However, the low secretion yield of EVs and the challenges of large-scale production remain the main barriers to their extensive clinical use. METHODS AND RESULTS : This review explores recent strategies to enhance EV production in cell culture systems, focusing on chemical stimulation, mechanical stimulation, and structural stimulation. First, we review chemical stimulation strategies for modulating culture conditions using chemical stimulation, including nutrient composition, pH, temperature, oxygen levels, intracellular cholesterol, and oxidative stress. Second, we examine mechanical stimulation strategies, including shear stress, irradiation, and ultrasound. Third, we explore structural stimulation strategies, such as three-dimensional (3D) culture systems involving spheroid-based culture, as well as the use of bioreactors and scaffolds. In addition, cell-derived nanovesicles containing cell membrane and cellular component, which can be more easily mass-produced compared to EVs, are proposed as an alternative to EVs. CONCLUSION : Future research should focus on developing cost-effective and scalable EV production methods while improving purification techniques to ensure a high yield without compromising functional integrity. Moreover, integrating optimized stimulation strategies—such as refining 3D culture systems, bioreactor designs, and mechanical stimulation methods—could further enhance EV secretion. Addressing these challenges is essential for advancing EV-based applications in both research and clinical practice.

Osteoporosis (OP) is a progressive bone disease marked by reduced bone mass and microarchitectural deterioration, thereby increasing fracture risk. Current therapies only partly restore bone quality and often cause side effects with long-term use. Recent studies highlight exosomes, a subtype of extracellular vesicles, as key regulators of bone remodeling with promising regenerative potential. However, their role in osteoporosis remains underexplored. This review aims to investigate how the established role of exosomes in bone regeneration may inform novel therapeutic strategies for osteoporosis. By linking general bone repair mechanisms with osteoporotic pathology, it evaluates the translational potential and limitations of exosome-based interventions. Exosomes derived from mesenchymal stem cells, osteoblasts, osteoclasts, and macrophages regulate bone homeostasis by modulating osteogenesis, osteoclastogenesis, and immune responses. Their regenerative effects in non-osteoporotic settings are well documented. However, challenges such as exosome heterogeneity, rapid clearance, and poor targeting efficiency impede their direct application in osteoporosis. Recent bioengineering approaches, including osteogenic RNA or protein loading and surface modifications for bone targeting, show promise. Moreover, combining exosomes with immunomodulatory or synergistic therapies may further enhance their efficacy. Despite these advances, gaps persist in standardizing isolation techniques, ensuring batch consistency, and scaling up production for clinical use. This review consolidates current knowledge and outlines directions for adapting exosome-based bone regenerative strategies to osteoporosis treatment.

Human adipose-derived stem cells (hASCs) have a capacity to undergo adipogenic, chondrogenic, and osteogenic differentiation. Recently, hASCs were applied to various fields including cell therapy for tissue regeneration. However, it is hard to predict the direction of differentiation of hASCs in real-time. Matrix metalloproteinases (MMPs) are one family of proteolytic enzymes that plays a pivotal role in regulating the biology of stem cells. MMPs secreted by hASCs are expected to show different expression patterns depending on the differentiation state of hASCs because biological functions exhibit different patterns during the differentiation of stem cells. Here, we investigated proteolytic enzyme activity, especially MMP-2 activity, in hASCs during their differentiation. The activities of proteolytic enzymes and MMP-2 were higher during chondrogenic differentiation than during adipogenic and osteogenic differentiation. During chondrogenic differentiation, mRNA expression of MMP-2 and the level of the active form of MMP-2 were increased, which also correlated with Col II. It is concluded that proteolytic enzyme activity and the level of the active form of MMP-2 were increased during chondrogenic differentiation, which was accelerated in the presence of Col II protein. According to our findings, MMP-2 could be a candidate maker for real-time detection of chondrogenic differentiation of hASCs.